RESUMEN
This study investigated the effects of increasing the intensity and/or duration of aerobic training sessions on thermoregulatory responses in rats subjected to exercises in temperate and warm environments. Thirty-two adult male Wistar rats were divided into four groups: a control (CON) group and three groups that were subjected to an 8-week aerobic training, during which the physical overload was achieved by predominantly increasing the exercise intensity (INT), duration (DUR) or by increasing both in an alternate manner (ID). During the last week of training, the rats received an abdominal sensor implant to measure their core body temperature (TCORE) by telemetry. After the training protocol, the 32 rats were subjected to incremental speed-exercises in temperate (23 °C) and warm (32 °C) environments. The rats had their TCORE recorded while running on a treadmill, and the ratio between the increase in TCORE and distance traveled was calculated to estimate thermoregulatory efficiency. All training protocols increased the rats' thermoregulatory efficiency during the incremental-speed exercise at 23 °C; i.e., trained rats attained faster running speeds but unchanged TCORE at fatigue compared to CON rats. However, none of the load components of training sessions - intensity or duration - was more effective than the other in improving this efficiency. At 32 °C, the aerobic training protocols did not influence the exercise-induced thermoregulatory responses. Our data indicate that different progressions in aerobic training performed at temperate conditions improved thermoregulatory efficiency during incremental exercise in the same environment; this training-induced adaptation was not clearly observed when running in warmer conditions.
Asunto(s)
Regulación de la Temperatura Corporal/fisiología , Condicionamiento Físico Animal/fisiología , Animales , Masculino , Ratas Wistar , TemperaturaRESUMEN
This study investigated the effects of manipulating the load components of aerobic training sessions on the physical performance of rats. To achieve this purpose, adult male Wistar rats were divided into four groups: an untrained control (CON) group and training groups with a predominant overload in intensity (INT) or duration (DUR) or alternating and similar overloads in intensity and duration (ID). Prior to, during, and after 8 weeks of the control or training protocols, the performance of the rats (evaluated by their workload) was determined during fatiguing, incremental-speed treadmill running. Two additional incremental running tests were performed prior to and at the end of the protocols to measure the peak rate of oxygen consumption (VO2peak). As expected, the rats in the trained groups exhibited increased performance, whereas the untrained rats showed stable performance throughout the 8 weeks. Notably, the performance gain exhibited by the DUR rats reached a plateau after the 4th week. This plateau was not present in the INT or ID rats, which exhibited increased performance at the end of training protocol compared with the DUR rats. None of the training protocols changed the VO2peak values; however, these values were attained at faster speeds, which indicated increased running economy. In conclusion, our findings demonstrate that the training protocols improved the physical performance of rats, likely resulting from enhanced running economy. Furthermore, compared with overload in duration, overload in the intensity of training sessions was more effective at inducing performance improvements across the 8 weeks of the study.
Asunto(s)
Condicionamiento Físico Animal , Animales , Consumo de Oxígeno , RatasRESUMEN
This study aimed to evaluate brain temperature (Tbrain) changes in spontaneously hypertensive rats (SHRs) subjected to two different physical exercise protocols in temperate or warm environments. We also investigated whether hypertension affects the kinetics of exercise-induced increases in Tbrain relative to the kinetics of abdominal temperature (Tabd) increases. Male 16-week-old normotensive Wistar rats (NWRs) and SHRs were implanted with an abdominal temperature sensor and a guide cannula in the frontal cortex to enable the insertion of a thermistor to measure Tbrain. Next, the animals were subjected to incremental-speed (initial speed of 10 m/min; speed was increased by 1 m/min every 3 min) or constant-speed (60% of the maximum speed) treadmill running until they were fatigued in a temperate (25°C) or warm (32°C) environment. Tbrain, Tabd and tail skin temperature were measured every min throughout the exercise trials. During incremental and constant exercise at 25°C and 32°C, the SHR group exhibited greater increases in Tbrain and Tabd relative to the NWR group. Irrespective of the environment, the heat loss threshold was attained at higher temperatures (either Tbrain or Tabd) in the SHRs. Moreover, the brain-abdominal temperature differential was lower at 32°C in the SHRs than in the NWRs during treadmill running. Overall, we conclude that SHRs exhibit enhanced brain hyperthermia during exercise and that hypertension influences the kinetics of the Tbrain relative to the Tabd increases, particularly during exercise in a warm environment.